1,4-butanediol (1,4-BDO) and is a valuable chemical used industrially as a solvent and in the production of elastic fibres such as elastane/spandex, polybutyrate terephthalate and derivatives of gamma butyrolactone.
1,4-butanediol is produced industrially via a number of routes from petrochemical feedstocks, obtainable from fossil fuels. One industrial route requires the reaction of acetylene with two equivalents of formaldehyde followed by hydrogenation of the resultant 1,4-butynediol to form 1,4-butanediol. In an alternative process, propylene oxide is converted to allyl alcohol. The allyl alcohol is then hydroformylated to form 4-hydroxybutyraldehyde, which may be hydrogenated to form 1,4-butanediol. Another industrial process requires maleic anhydride as a starting material and proceeds via conversion to the methyl maleate ester and subsequent hydrogenation. Other traditional routes use butadiene, allyl acetate or succinic acid as starting materials.
1,4-butanediol may also be produced as a side-product in a method for making tetrahydrofuran (THF) by oxidizing n-butane to crude maleic anhydride followed by catalytic hydrogenation.
It is often the case that other desirable co-products, such as THF, γ-butyrolactone (GBL) and n-butanol are formed in processes that produce 1,4-butanediol. Such processes can be tailored to make more or less of each of these chemicals.
In recent years, increased efforts have focused on producing chemicals, including 1,4-BDO and the desirable co-products, from renewable feedstocks, such as sugar-based materials. U.S. Pat. No. 8,067,214 describes a biosynthetic pathway to produce 1,4-BDO directly from sugar using a non-naturally occurring microbial organism.
A further method for obtaining 1,4-butanediol and one or more of the desirable co-products (particularly THF) from non-fossil fuel based sources involves the decarboxylation of furfural and proceeds via an intermediate such as furan. Examples of reaction processes for achieving these steps can be found in Hoydonck, H. E., Van Rhijn, W. M., Van Rhijn, W., De Vos, D. E. & Jacobs, P. A. (2012) Furfural and Derivatives, in Ulmann's Encyclopedia or Industrial Chemistry (volume 16, pp 285-313), Wiley-VCH Verlag GmBH & Co. KGaA, Weinheim; Dunlop, A. P. and Peters, F. N., in The Furans Reinhold Publ. Co, 1953; K. J. Zeitsch, in “The Chemistry and Technology of Furfural and its Many By-products” Sugar Series 13, Elsevier, 2000; Lange, J-P, van der Heide, E, van Buijtenen, J., and Price, R.; Furfural—A Promising Platform for Lignocellulosic Biofuels; ChemSusChem 2012, 5, 150-166 and Watson, J. M., Ind. Eng. Chem. Prod. Res. Develop., 1973, 12(4), 310. Furfural may be obtained from hemicellulose via acid hydrolysis in the liquid phase as well as in the gas phase as described in WO 2002/22593 and WO 2012/041990.
Succinic acid is also available from bio-based resources, as described in Green Chem., 2009, 11, 13, and can be used as a starting material in the production of 1,4-butanediol as well as the other desirable co-products, such as γ-butyrolactone, n-butanol and tetrahydrofuran.
Many processes provide 1,4-BDO and co-products as products within an aqueous stream. Typically, the 1,4-BDO and whichever co-products are present are purified using an energy-intensive distillation process, which may be complicated by the presence of azeotropes.
It would, therefore, be advantageous to provide an improved method suitable for the recovery of at least 1,4-butanediol and its desirable co-products from aqueous streams.